(1) Field of the Invention
The present invention relates to a high-density fuel, and more particularly to a high-density and high energy liquid fuel used for jet propulsion of rockets or jet engines.
(2) Description of the Prior Art
In a rocket or a jet engine for a turbo jet, a ram jet, a pulse jet or the like, a high-energy liquid fuel is used. In order to increase the propulsion force of such a jet engine, a fuel having a high combustion energy per unit weight, i.e., a high-density and high-combustion heat release liquid fuel is required. The liquid fuel for jet engines is fed to a combustion chamber through a pipe, but since a flying object carrying the jet engine flies at a high altitude and since liquid oxygen is also used, the liquid fuel will be exposed to an extremely low temperature. Therefore, other requirements of the liquid fuel for jet engines are to have a low freezing point and a low pour point, and to possess a moderate viscosity even at a low temperature. Further, it is also necessary that the liquid fuel for jet engines has no unsaturated bonds and can be stored stably for a long period of time.
As such liquid fuels for jet engines, there have been known exo-tetrahydrodicyclopentadiene (JP-10; Japanese Patent Publication No. 20977/1970) which can be prepared by the isomerization of hydrogenated dicyclopentadiene with an acid catalyst, and a compound which can be prepared by hydrogenating a dimer of norbonadiene (RJ-5; U.S. Pat. No. 3,377,398). The aforesaid JP-10 is good in fluidity at a low temperature but is low in density, and its heat of combustion per unit volume is disadvantageously small. On the other hand, the aforesaid RJ-5 has a large heat of combustion per unit volume, but its fluidity at a low temperature is poor. Moreover, the RJ-5 has the drawback of being difficult to synthesize and being expensive.